Analyte detection is an important component in biotechnology, analytical chemistry, analysis of environmental samples, and medical diagnostics. Certain types of detection assays, such as fluorescence-based assays, are capable of providing detailed pictures of where fluorescent molecules are localized in tissues and cells. In particular, fluorescence-based assays exhibit exceptional sensitivity, detecting small concentrations of fluorescent molecules.
In addition, direct, minimally invasive monitoring of in vivo physiological conditions presents a route to determine health status in real time and address needs as they arise. Continuously monitoring sodium in vivo addresses multiple diseases and could prevent clinical complications during certain procedures. Sodium imbalances may lead to hypernatremia (Adrogue H J, Madias N E (2000) N Engl J Med 342:1483-1499) or hyponatremia (Adrogue H J, Madias N E (2000) N Engl J Med 342:1581-1589)—the most common electrolyte disorder. Monitoring sodium may provide an insight into the progression of subarachnoid hemorrhage or syndrome of inappropriate antidiuresis (Benvenga S (2006) Nat Clin Pract Endocrinol Metab 2:608-609; Ellison D H, Berl T (2007) N Engl J Med 356:2064-2072). However, to provide continuous monitoring, sensors need to be small enough to have a rapid response to changes in concentration yet be large enough to reside at the sight of administration without diffusing away or being endocytosed/phagocytosed by cells.
However, the only commercially available methods to measure analytes are through blood withdrawals and detection through either a glucometer or ELISA detection kit. These approaches require the removal of blood and can only be made when blood is drawn. Furthermore, presently available approaches utilize sensors that are insufficient for in vivo monitoring of analytes because the sensors do not remain at the site of administration and therefore do not provide an opportunity to detect the sensors.
Previous in vivo studies with fluorescent nanosensors were limited because of sensor diffusion away from and cellular uptake at the injection site. Alternative approaches that include altering sensing geometry into microworms and gel encapsulation of sensors prolonged in vivo sensing, but could not be sufficiently mass produced or had a limited lifetime, respectively.
Therefore, there is a need for devices, compositions and methods for the inexpensive and rapid assaying of biological, environmental, and chemical samples. Moreover, there is a need for sensing devices that can be mass produced and devices that limit cellular uptake and diffusion of the sensors in vivo.